Work from our laboratory has demonstrated that the cytochrome P450 epoxygenases metabolize arachidonic acid (AA) to a novel group of fatty acid epoxides called EETs. These compounds have been shown to possess potent biological activities including effects on vascular and airway smooth muscle and modulation of ion transport. We hypothesize that: (1) the EETs and their hydration products, the DHETs, play important roles in cell and organ physiology; and (2) aberrant expression of the P450 epoxygenase genes leads to cell and organ dysfunction. Current research in the Clinical Studies Section involves: (1) characterization of the human cytochrome P450 AA epoxygenase metabolic pathway at the cellular, biochemical , and molecular levels; (2) evaluation of the roles that the EETs and DHETs play in cell and organ physiology; and (3) examination of this enzymatic pathway in selected human diseases (e.g. cancer, asthma, hypertension). Over the past year, we have cloned a full length cDNA (CYP2J2) coding for a novel human cytochrome P450 arachidonic acid epoxygenase. Northern analysis of RNA prepared from various human tissues revealed that CYP2J2 displayed an unusual tissue distribution with highest levels in human heart and intestine. The recombinant protein was expressed in insect cells, purified to homogeneity, and shown to catalyze the NADPH-dependent regio-and stereoselective metabolism of AA to biologically active EETs as primary reaction products. The in vivo significance of CYP2J2 was confirmed by demonstrating, for the first time, the presence of EETs in human heart and intestine using HPLC/GC/MS techniques. Polyclonal antibodies raised against the purified, recombinant protein were used to confirm that CYP2J2 protein was highly expressed in heart and intestine. current efforts are focused on the following: (a) localization of expression of human CYP2J2 to specific cell types in heart, intestine, and kidney; (b) functional significance of epoxygenase gene products in cardiac and intestinal physiology; and (c) regulation of human CYP2J2 gene expression.